Aqua-Hot 600 series User manual

USE & CARE GUIDE
600SERIES
600D and 675D

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Journey in Comfort
Thank you for equipping your RV with an Aqua-Hot hydronic heating system! We
value your business and are grateful for the trust you have placed with Aqua-Hot
Heating Systems Inc. Our customers are top priority and we are committed to
providing best-in-class products, service, and support.
We understand how important comfort is to you as a motor home owner; there-
fore, we have designed a heating system to significantly improve all of your comfort
levels while on the road. Additionally, the Aqua-Hot hydronic heating system is a low
emission, fuel efficient system that adds thousands of dollars to your motor home.
We know you must be eager to get underway, but take time to read the entire
Use & Care Guide and understand your Aqua-Hot unit. This guide should be main-
tained in legible condition and kept in a safe, accessible location for future review.
Should you have any suggestions how we can better serve you, please do not
hesitate to contact us at 800-685-4298 or 303-651-5500.
The Aqua-Hot hydronic heating system is protected by the finest warranty in the
industry (read it on page 19).
IMPORTANT NOTE:
 A qualified installer or service technician must perform equipment installation
or service. Contact Aqua-Hot for Factory Authorized Service Centers or Certified
Technicians located near you: www.aquahot.com/ service-help: 800-685-4298
or 303-651-5500.
 Warranty work must be performed by an Aqua-Hot Factory Authorized Service
Center.
IMPORTANT NOTE:
 Your on-product identity label contains specifications of your unit. Factory set-
tings may be adjusted by your RV manufacturer, confirm final setting with your
dealer.
WARNING:
 If the information in this guide is not followed exactly, a fire or explosion may
result, causing property damage or personal injury.

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Comfort Zones
Comfort Zone #1: Comfortable Cabin Heat.
Get heat where you want it, when you want it! The Aqua-Hot system heats by zones. Therefore, your bedroom, living room, and
bathroom can be custom temperatures. Don’t hesitate to crank up the heat because the Aqua-Hot system doesn’t remove
moisture from the air. From now on, you will have to blame the dry skin and itchy eyes on Mother Nature!
Comfort Zone #2: Quiet Operation
Say goodbye to rude awakenings from the forced air furnace, you’re an Aqua-Hot owner now! The Aqua-Hot is quiet when op-
erating, so you’ll never have to turn up the TV, yell across the room, or have an interrupted night of sleep again due to your
heating system.
Comfort Zone #3: Continuous, On-Demand Hot Water
Take long, guilt free showers knowing there is no recovery time for the next shower or load of laundry. The freedom to take a
shower when you want makes your RV experience feel much more like home.
Comfort Zone #4: Low Emissions
Aqua-Hot’s new low emission systems are fumeless and odorless. It’s good for you,
good for your neighbor, and good for the environment.
Comfort Zone #5: Over 160 Factory-Trained Service Centers
You won’t need to service your Aqua-Hot often, but when you do, you can be confident in our Certified Service Centers that are
close by and trained to assist you with all of your Aqua-Hot specific needs.
Comfort Zone #6: Adds Value
The NADA Recreational Vehicle Guide lists Aqua-Hot as adding thousands of dollars to the value of an RV. That value will pay
off when it’s time to trade up or sell.
Comfort Zone #7: Low Fuel Costs
There’s no need to burn propane each time heat or hot water is needed. Aqua-Hot’s TribridHot technology powers the Aqua-
Hot system by pulling heat from one or a combination of heat sources. When shore power is available, simply plug it in. When
dry-camping or in very cold conditions, use the Diesel Burner.

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Contents Caution Notes
As you read this Information, take particular note
of the NOTICE, CAUTION, WARNING and
DANGER symbols when they appear. This infor-
mation is important for safe and efficient use of
the Aqua-Hot equipment.
NOTICE signals a situation where potential dam-
age to the equipment could occur.
CAUTION signals a situation where potential harm
or risk of minor or moderate injury could occur if
you do not follow instructions
WARNING signals a hazardous situation where
potential harm, risk of serious injury or death
could result if you do not follow instructions
DANGER signals a situation where immediate risk
of serious injury or death will result if you do not
follow instructions
NOTE: In addition, this manual may indicate an
IMPORTANT NOTE that highlights information that
is especially important.
Introduction
About the Aqua-Hot Hydronic Heating System .....................5
Aqua-Hot Hydronic Heating System Reference .................... 6
Operating Instructions
Activating the Aqua-Hot Heating System .............................. 7
Operating Zone Thermostats.................................................8
Using the Domestic Water Heating System.......................... 8
Aqua-Hot Operational Flow Chart.......................................... 9
Troubleshooting
General Information.............................................................10
Electronic Controller Diagnosis ...........................................10
Tempering Valve ..................................................................11
Maintenance
Monthly Maintenance..........................................................12
Replenishing the Antifreeze/Water Solution ......................12
Annual Maintenance............................................................12
Winterization
Winterizing the Domestic Water Heating System ..............13
De-Winterizing the Domestic Water Heating System.........13
Appendices
Appendix A: Antifreeze Types ..............................................14
Appendix B: Antifreeze Mixture/Water Quality ...................14
Appendix C: Antifreeze Terms and Mixture Ratio ...............14
Appendix D: Measuring Propylene Glycol
Using a Refractometer....................................16
Owner’s Service Log ............................................................18
Warranty
Limited Warranty Statement ...............................................20
Contents & Cautions

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IMPORATANT NOTE: Read all instructions before using this
appliance.
 Read this Use & Care Guide before using your Aqua-Hot
Heating System to reduce the risk of injury to persons
or damage to equipment.
 Have your dealer show you the location and operation
of all switch operations and valve settings.
 Do not repair or service the system, unless specifically
recommended in the literature accompanying the Aqua-
Hot product. All service should be referred to a qualified
technician.
 An interlock switch prevents the Aqua-Hot heater from
operating when the cover is not installed in the correct
position.
 Propylene glycol based antifreeze, “Generally Recog-
nized as Safe” by the FDA, must be utilized for anti-
freeze and water heating solution.
 Interior heat can still be used once the water heating
system has been drained and winterized.
 Use propylene glycol “Generally Recognized as Safe” RV
and Marine antifreeze specifically for “winterizing” ap-
plication ONLY.
CAUTION:
 The hot water temperature is set at the mixing valve to
120°F/ 48.9°C at the factory.
 DO winterize the heating system when freezing temper-
atures are expected to avoid serious damage to the hot
water system.
 DO NOT operate the burner or electric heating element
without antifreeze or water heating solution in the boil-
er tank to avoid damage to the heater.
 Aqua-Hot’s exhaust is hot. DO NOT park in dry areas
when operating to avoid fire and injury to persons.
 At maximum operating temperatures, the coolant will
be very hot and scalding hot vapor or coolant may re-
sult in serious burns or injury.
 Before cleaning or servicing, disconnect all power sup-
plies.
 The heater must be switched OFF when refueling.
 DO NOT operate the Aqua-Hot’s diesel-burner inside an
enclosed building.
Safety Instructions & Precautions
The Unit

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Aqua-Hot Heating System Features
The Aqua-Hot Heating System is a Low Emissions Hy-
dronic Heating System (heating with hot water) that signifi-
cantly improves your level of comfort, decreases harmful
emissions released into the atmosphere, and adds thou-
sands of dollars to your RV.
The Aqua-Hot Heating System is three systems in one:
1. Interior Heating System: provides quiet, comfortable
interior heat with independent temperature zones that
provide cabin-wide even temperatures.
2. Bay Heating System: keeps pipes and tanks from freez-
ing in the bay storage area.
3. Tank-less Hot Water System: provides a steady flow of
continuous hot water.
4. Engine Preheating System: reduces engine wear
caused by cold starting by preheating the engine from
30°F to 90°F in one hour.
The Aqua-Hot System is powered by TribridHot™ technology
and uses one or a combination of the following sources:
1. The 120 Volt-AC Electric Element: When plugged into
shore power, the electric element lets you use the pow-
er you are already paying for to provide heat and meet
your light duty hot water needs.
2. The Diesel Burner: This is the Aqua-Hot’s most powerful
heat source and provides all of heating and hot water
needs in cold temperatures or dry camping.
3. The Vehicle’s Engine: When driving or idling, the en-
gines surplus heat is transferred to the Aqua-Hot provid-
ing interior heat and limited hot water without burning
any other fuel.
NOTE: This Aqua-Hot product utilizes a propylene glycol
based antifreeze and water heating solution. This propylene
glycol based solution is a boiler type antifreeze that is
“Generally Recognized as Safe” (GRAS) by the FDA. For
additional information regarding this “GRAS” antifreeze
product, please reference the Care & Maintenance section
of this guide, contact the Aqua-Hot Heating Systems Tech-
nical Support Department at 1-800-685-4298, or visit the
web site at www.aquahot.com.
The product label
attached to the
Aqua-Hot
provides a ready
reference to
specifications, test
standards, and
important safety
notices.
600D and 675D Features
NOTE: Service parts and accessories are available through
Aqua-Hot Factory Authorized Service Center or at
www.aquahot.com.

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Cut-Away Diagrams
Aqua-Hot Heating System Features
1. AC Wiring Ports
2. Access Cover
3. Air Release Valve
4. Diesel Burner
5. Diesel Burner Controller
6. Diesel Fuel Inlet/Outlet Ports
7. Domestic Water Access Panel
8. Domestic Water Inlet/Outlet Ports
9. Drain Valve
10. Engine Preheat Inlet/Outlet Ports
11. Engine Preheat Pump
12. Expansion Tank Connection
13. Heating Zone 1
14. Interlock Switch
15. Tempering Valve
16. Wiring Harness Port
17. Zone 1 Circulation Pump
18. Zone 1, 2, and 3 Inlet Ports
19. Zone 1, 2, and 3 Outlet Ports
20. Zone 2 Circulation Pump
21. Zone 3 Circulation Pump
1
5
7
16
17
14
11
9
10
3
4
6
8
12
13
19
18
2
5
20
16
7
15
21
17

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Aqua-Hot Heating System Features
Do not operate the diesel-burner and/or electric element
without the antifreeze and water heating solution in the Aq-
ua-Hot’s boiler tank. Failure to do so will cause serious dam-
age to the heater.
Switches:
The Aqua-Hot heating system is controlled by two switch-
es, the burner switch and the electric element switch. This
style of Aqua-Hot is equipped with an Engine Preheat ele-
ment as well. When one or both the burner or electric ele-
ment switches are in the ON position, it will supply the nec-
essary heat to the boiler tank. Keep in mind that the Aqua-
Hot must be at operating temperature for the heating zones
and hot water to function properly. Please contact the spe-
cific motorhome dealer for the exact location of switch oper-
ations.
The Aqua-Hot interior switch panel has a high/low switch
that works in conjunction with the electric element switch.
 Low Switch- Turn the electric element switch ON in con-
junction with the high/low switch placed in the LOW
position. Reference Figure 1. This procedure will acti-
vate one of the two 120 VAC Electric Heating elements
and the indicator lights located on both the electric ele-
ment and the high/low switches. Allow 1-2 hours for the
Aqua-Hot system to reach operating temperature.
 High Switch- Turn the electric element switch ON in con-
junction with the high/low switch placed in the HIGH
position. Reference Figure 1. This procedure will acti-
vate both the 120 VAC Electric Heating Elements and
the indicator lights located on both the Electric Element
and the high/low switches. Allow half an hour to an
hour for the Aqua-Hot System to reach operating tem-
perature. The electric heating elements are a secondary
heat source for heating both the interior and the do-
mestic hot water during low heating demand situations.
This heat source should be used when moderate tem-
peratures exist and/or when there is a high demand for
domestic hot water.
Thermostats:
The interior room thermostat can be set at the desired
temperature; therefore, whenever the interior of the room
“calls for heat”, the Aqua-Hot’s circulation pump and interior
heat exchanger fans will be activated. The fresh water ther-
mostat controls the bay heating area and should NOT be set
below 40°F, to prevent freezing of the domestic water stor-
age system. Please contact the specific motor home dealer
Figure 1

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Heating Operation
Overview:
The heating features are powered by a 12 Volt-DC diesel
-burner and two 120 Volt-AC electric heating elements.
These two heating elements maintain the temperature of
the Aqua-Hot’s antifreeze and water heating solution to
provide hot water and heat to the motor home.
 Diesel–The diesel-burner is the Aqua-Hot’s primary
and most powerful heat source and provides all of the
heating and hot water needs when cold temperatures
exist and/or when there is a high demand for hot wa-
ter. It can be activated by turning the burner switch in
the ON position. Reference Figure 1.
 Electric–The electric element is the Aqua-Hot’s sec-
ondary heat source and can be used when plugged
into shore power. The electric element provides heat
when moderate temperatures exist (50°F or higher)
and/or when there is a low demand for hot water. It
can be activated by turning the electric switch in the
ON position. Reference Figure 1.
 Engine Preheat- In order to use the Engine Preheat
element on the Aqua-Hot system, both the diesel-burner
AND the engine preheat switch must be turned ON. Al-
low the engine preheat element to function for one hour
before starting the vehicle's engine. Reference Figure 1.
Controlling Heat Levels:
The interior room thermostat can be adjusted at the de-
sired temperature and will automatically be activated to
maintain the temperature of the interior. Keep in mind that
the diesel and/or electric element switch on the interior
switch panel must be in the ON position for the heat to op-
erate.
Control/Balancing Heating Zones:
Set the interior room thermostat for each independent
heating zone at the desired temperature. This feature al-
lows you to customize various temperatures on each heat-
ing zone throughout your motor home.
Using the Water Heating System
General Information:
The Aqua-Hot system is known as an on-demand hot
water heating system because hot water is not stored within
the motor home. Instead, when the burner and/or electric
element switch is ON and the Aqua-Hot is at operating tem-
perature, the water is automatically heated as it is being
used. Therefore, simply open an hot water faucet once sys-
tem is up to operating temperature, and a continuous sup-
ply of hot water will be present within a few seconds.
The Aqua-Hot’s exhaust is HOT! Do NOT park is areas where
dry conditions exist (i.e., grassy, dry fields). Do NOT operate
the diesel-burner inside an enclosed building. The heater
must be switched OFF when refueling.
Operation Instructions:
To operate the Aqua-Hot hot water system, you will need
to locate the interior switch panel located inside your motor
home. If you are unable to locate the switch panel, contact
your dealer to guide you in the location and operation of all
switch operations. Once you have located the interior switch
panel, turn the burner switch ON. This action will activate
the diesel-burner and the indicator light located adjacent to
the diesel-burner switch. Allow 10-20 minutes for the Aqua-
Hot system to reach operating temperature. Please note
that the diesel-burner is the primary heat source for heating
the interior and hot water.
To operate the electric heating element, turn the electric
switch ON. This action will activate the 12 Volt-AC electric
heating element and the indicator light located adjacent to
the electric switch. Allow 1-2 hours for the Aqua-Hot system
to reach operating temperature. Be sure to activate the
electric element switch for maximum water capacity. Figure
1 is an example of an interior switch panel.
Interior Heating Operation
Hot Water Operation
NOTE: The motor home must be connected to shore power
or the generator must be running in order to activate the
electric heating element.

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Heat source is selected from the
Interior Switch Panel.
Diesel-Burner is activated by
the Burner switch.
Electric Heating Element is
activated by the Electric
switch.
The cooled antifreeze and water heat-
ing solution is returned to the boiler
tank to be reheated.
Heating Zone Thermostat
calls for heat.
The heated antifreeze and
water heating solution flows
through the Hydronic Heating
System transferring heat to
the heat exchanger, which is
then transferred to the sur-
rounding zone.
A hot water faucet (e.g., kitchen
sink, shower, etc.) is opened.
Continuous hot water is
supplied to the faucet.
“Engine Preheat” switch on
the Interior Switch Panel is
activated.
The engine’s coolant is circu-
lated through the Aqua-Hot’s
internal Engine Preheat Sys-
tem, where the heat from the
Boiler Tank is transferred to
the engine’s coolant.
The Boiler Tank heats the
antifreeze and water heat-
ing solution to 190°F.
Operational Flowchart

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Overview:
The Aqua-Hot system requires minimal maintenance if
monthly, annual, and proper winterization procedures are
followed accurately. It is extremely important to follow the
instructions below precisely and carefully to receive the best
results and promote the longevity of your Aqua-Hot. Monthly
maintenance to the Aqua-Hot requires a visual check of the
antifreeze and water solution to make sure it’s at the correct
operating level. Annual maintenance to the Aqua-Hot re-
quires a replacement of two parts on the diesel-burner, the
fuel nozzle and fuel filter. Winterization of an Aqua-Hot sys-
tem prepares a motor home for storage during the winter
months to prevent freezing pipes and other critical damage.
When the Aqua-Hot is at maximum operating temperature,
the coolant will be very HOT! If the Aqua-Hot’s heating sys-
tem is accessed, scalding hot vapor or coolant could result.
Before cleaning or servicing, disconnect all power supplies.
Monthly:
It is extremely important to check the Aqua-Hot’s anti-
freeze and water heating solution to ensure it is at the prop-
er level for operation. This task can be done by visibly check-
ing the coolant level in the Aqua-Hot’s expansion tank. At
maximum operating temperature, the antifreeze and water
heating solution should be at the level marked “HOT” on the
expansion tank. The coolant level should be checked ONLY
when the Aqua-Hot is at maximum operating temperature.
Therefore, this procedure should be done immediately after
the diesel-burner cycles OFF. Reference figure below. If it
needs refilling, reference “Fluids” in the Care & Maintenance
section.
Expansion Tank
Cap
Fluid will reach
Expansion Tank
line when HOT
Care & Maintenance
Annual:
In order to keep the Aqua-Hot running at its full potential,
it’s highly recommended to have the diesel-burner tuned up
annually. This tune up consists of a new fuel nozzle (Part
Number: FLX-013-150) and fuel filter (Part Number: FLE-
120-100). To ensure maximum diesel-burner performance,
always use the recommended fuel nozzle and fuel filter
when replacing these parts. Reference the Aqua-Hot’s Ser-
vice and Parts Manual for spare parts information and de-
tailed replacement attachments.
Winterization:
When it’s time to store a motor home for the winter
months or when freezing temperatures are expected, it’s
crucial to properly winterize the Aqua-Hot to avoid serious
damage, requiring a complete system replacement not cov-
ered under the Aqua-Hot Limited Warranty Statement. The
process of winterization consists of completely draining the
domestic water from the system and pumping RV winteriza-
tion antifreeze through to flush out the system.
Not winterizing the Aqua-Hot when freezing temperatures
are present will result in SERIOUS damage to the Aqua-
Hot’s Domestic Water Heating System. Also, be sure to use
the FDA approved, “GRAS” rated antifreeze for winteriza-
tion.
Please follow these instructions carefully when winterizing
the Aqua-Hot’s hot water heating system:
1. Completely drain the fresh water storage tank.
2. Disconnect the domestic water demand pump’s suction
line from the fresh water storage tank.
3. Attach an adequate piece of hose onto the suction side
of the domestic water pump.
4. Place the opposite end of the hose into an adequate
supply of the RV antifreeze, “GRAS” by the FDA and al-
low this to pump through the system.
5. Open and close all interior and exterior water faucets,
one at a time, until ONLY pure RV antifreeze is present.
Perform this procedure for both hot and cold faucets.
6. Remove the hose from the RV antifreeze and reconnect
the domestic water demand pump’s suction line to the
fresh water storage tank.

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Care & Maintenance
De-Winterization:
To de-winterize the Aqua-Hot system, completely fill the
fresh water storage tank. Open and close the interior and
exterior faucets, one at a time, until only clear water is pre-
sent.
Disinfecting the Water System:
Aqua-Hot systems contain copper tubing and are not com-
patible to prolonged exposure to sodium hypochlorite
(bleach or liquid bleach). Using products containing bleach,
including water refreshers, may cause corrosion of the
domestic water coil, resulting in a catastrophic failure of
the Aqua-Hot system by creating leaks that cannot be
repaired. This damage is not covered by the Aqua-Hot war-
ranty.
If disinfecting the hot water heating system be sure to follow
NFPA 1192 Standard on Recreational Vehicles’
“Instructions for Disinfection of Potable Water Systems.”
These instructions can be found by visiting the National Fire
Protection Association online at www.nfpa.org.
Fluids:
Overview:
When the antifreeze and water heating solution needs
replenishing, remove the expansion tank’s cap and fill to
the “HOT” level mark. When refilling, open the air release
valve located on the expansion tank connection to release
air pockets. Be sure the valve is closed when finished by
hand tightening.
Types:
Due to the significant impact of various types of anti-
freeze on the Aqua-Hot system, it is necessary to provide a
thorough explanation regarding what should and should
not
be used. It’s very important use the correct type of anti-
freeze for adequate operation and condition of the Aqua-
Hot System. The necessary type of antifreeze is propylene
glycol based “boiler” type deemed “Generally Recognized
as Safe” by the FDA. Propylene glycol is a safer alternative
to the more toxic ethylene glycol antifreeze.
RV and Marine antifreeze types are propylene glycol
based, but formulated specifically for “winterizing” applica-
tion ONLY. Although RV and Marine antifreeze are often
“Generally Recognized as Safe” by the FDA, it should never
be used in the Aqua-Hot System because it’s not formulat-
ed to transfer heat, which is absolutely essential for the
functionality of the Aqua-Hot.
Automotive Antifreeze/Coolant types of antifreeze are
propylene glycol based and formulated specifically to pro-
tect the automotive engines against, corrosion, freezing
temperatures, and overheating. In addition, they have ex-
cellent heat transfer and thermal conductivity characteris-
tics. Although these types of antifreeze are considered less
toxic and safer than ethylene glycol, they are not
“Generally Recognized as Safe” by the FDA. Therefore,
they must be marked with “harmful if swallowed” warning
label. Due to the potentially hazardous properties, Automo-
tive Antifreeze/Coolant should NEVER be used in an Aqua-
Hot System.
Mixture Recommendations:
To ensure maximum performance and longevity of the
Aqua-Hot system, it has been determined to use distilled,
de-ionized, or soft water in commination with concentrated
propylene glycol for the antifreeze and water heating solu-
tion. Concentrated propylene glycol should be diluted with
high-quality (distilled, diluted, or soft) water, which is 80
ppm or less in total hardness. In order to find this infor-
mation, the local water agency should have up-to-date wa-
ter quality reports, which will indicate if the local tap water
meets the requirements.
Hard water possesses a high-level of calcium and magne-
sium ions, which deplete the propylene glycol antifreeze’s
corrosion inhibitors. This causes the antifreeze and water
heating solution to turn acidic, which can corrode the Aqua

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Care & Maintenance
-Hot’s boiler tank and associated components prematurely.
Keep in mind that using high-quality water is only necessary
for mixing concentrated propylene glycol antifreeze with wa-
ter. Suppliers of premixed antifreeze are responsible to use
distilled, de-ionized, or soft water when preparing their anti-
freeze, s consumer shouldn’t have to worry about it.
Mixture Ratios:
Technical Information:
Propylene glycol based (PPG) antifreeze has three major
functions including freeze, boiling, and rust/anti-corrosive
protection. PPG antifreeze solution is also primarily respon-
sible for heat transfer; however, propylene glycol itself does
not have acceptable heat transfer characteristics. Therefore,
water is added to the mixture because it is an excellent heat
conductor. PPG antifreeze solution, mixed with water that is
30-50% propylene glycol is recommended to provide the
best performance combination. If the antifreeze and water
heating solution contains over 70% propylene glycol, the
freezing point is actually increased, resulting in less freeze
protection. A perfect 50/50 mixture of water to propylene
glycol, “GRAS” by the FDA antifreeze is recommended, which
will result in a freeze point of –28°F and a boiling point of
approximately 222°F. Please reference the
graphical representation regarding the percentage of anti-
freeze to water and how it directly affects the solution’s
freezing point.
Freeze and Burst Point:
Antifreeze solution lowers the freezing point of any liquid
to which it has been added by preventing the formation of
crystals. However, as ambient temperature continues to
decline, the water in the solution will attempt to attain a
solid state. The point at which the water begins to solidify is
called the “freeze point”. Although the water solution has
begun to freeze, producing a “slushy” consistency, the anti-
freeze in the solution will continue to combat normal expan-
sion of the solution as it freezes. The point in which the so-
lution can begin to expand, due to colder temperatures, is
called the “burst point”. Once the solution reaches the burst
point, the potential is present for ruptured pipes and other
components. The burst point of the antifreeze and the wa-
ter heating solution is dependent upon the brand of propyl-
ene glycol antifreeze employed.
Boiling Point:
The Aqua-Hot utilizes the propylene glycol based (PPG)
antifreeze and water heating solution as a transportation
means for the heat produced from the internal processes.
The PPG antifreeze solution absorbs the heat created until
its boiling point is reached. At this point, the liquid turns to
gas and is expelled to prevent the heating system from
overheating. Each time the boiling point is reached, a loss
of efficiency occurs because the heat produced is expelled
rather that utilized for the function of the heating system.
Therefore, a higher boiling point is desired in order to com-
bat the loss of efficiency, which allows the antifreeze to
transport the heat created from the
internal process throughout the motor
home where it can be utilized produc-
tively rather than dissipating due to its
change from a liquid to a gas.
Rust and Anti-Corrosive Inhibitors:
Another major function of antifreeze
solution is to provide protection to the
internal metal components of the Aqua
-Hot hydronic heating system for corro-
sion and rust. Antifreeze is able to pre-
form this function by the addition of
rust and anti-corrosive inhibitors,
which are designed specifically to acti-
vate in a water solution.

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Eyepiece
Calibration Screw
Daylight Plate
Assembly
Main Prism
Assembly
Aqua-Hot Part Number MSX-907-162
Basic Operation
Step 1:
Open daylight plate, and place 2 to 3
drops of the sample on the main
prism. Close the daylight plate so the
liquid sample spreads across the en-
tire surface of the prism without air
bubble or dry spots. Allow the sample
to rest on the prism for approximately
30 seconds before going to step 2.
(This allows the sample to adjust to
the ambient temperature of the refrac-
tometer).
Step 2:
Hold daylight plate in the direction of a light
source and look into the eye piece. You will
see a circular field with graduations down
the center (you may have to focus the eye-
piece to clearly see the graduations). The
upper portion of the field should be blue,
while the lower portion should be white.
Step 3:
Take the reading where the boundary
line of the blue and white cross the
graduate scale. The scale will provide a
reading of the freezing point of anti-
freeze solution and the propylene gly-
col concentration. Clean the prism
carefully using a damp soft cloth. Do
NOT immerse in water.
NOTE: Refractometers may have more than one
scale. Make sure you are reading the scale
marked “Propylene” for measuring the antifreeze
solution in the Aqua-Hot System.
Use extreme caution in gathering your antifreeze sample.
When draining the Aqua-Hot heating system, extremely hot
liquid may be in the boiler tank and could cause personal
injury.
Care & Maintenance
Using the Refractometer to Test Antifreeze Sample

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Troubleshooting Guide
Should the Aqua-Hot Hydronic Heating System fail to
operate, complete the following checks:
1. Verify that the Aqua-Hot’s access cover is securely in-
stalled. Reference page 6 (part #2). The Aqua-Hot Hy-
dronic Heating System will not operate if the access
cover is not fully installed.
2. Ensure that the vehicle’s fuel tank contains a sufficient
level of fuel. The Aqua-Hot system will not operate if
the fuel level is at or below 1/4 tank.
3. Ensure that the Aqua-Hot’s boiler tank has an ade-
quate supply of antifreeze and water heating solution
by checking the level at the Expansion Tank. If the level
is low, reference the Maintenance section of this guide
for refilling instructions.
4. Check the Aqua-Hot’s electronic controller for any RED
lights indicating a fault condition.
If the Aqua-Hot Heating System’s failure to operate is
not resolved with the aforementioned checks, please con-
tact the Aqua-Hot Heating Systems Technical Support De-
partment at 1-800-685-4298 for additional assistance or
visit the web site at www.aquahot.com.
If the Aqua-Hot’s Diesel-Burner switch “Indicator Light”
does not illuminate and the Diesel-Burner is not function-
ing, locate the electronic controller and check the following:
1. Check the Aqua-Hot’s electronic controller for any RED
lights indicating a fault condition. Reference Figure 2.
2. Check for loose wire connections on the electric con-
troller’s terminal strips/plugs. When checking for loose
terminal strips/plugs, remove the electronic controller
faceplate by unscrewing the four cover screws.
3. Remove the Aqua-Hot’s access cover and check for
loose plug connections on the Diesel-Burner controller
unit. Reference page 6 (part #2).
4. Ensure the vehicle’s fuel tank has a sufficient level of
fuel.
5. If the Aqua-Hot still fails to operate, please contact the
Aqua-Hot Heating Systems Technical Support Depart-
ment at 1-800-685-4298 or visit the web site at
www.aquahot.com.
NOTE: An interlock switch prevents the Aqua-Hot from op-
erating when the cover is not installed and properly in
place.
General Information Electronic Controller Diagnosis
Low Tank-Level Cutoff Indicator Light:
This indicator light will illuminate RED when either the
120 Volt-AC electric heating element and/or Diesel-Burner
have automatically shut down due to low antifreeze and
water heating solution level inside the Aqua-Hot’s boiler
tank. This fault will automatically reset when the low level
condition is corrected.
Low Battery Voltage Fault Indicator Light:
This indicator light will illuminate RED and the Diesel-
Burner will shut down whenever the 12 Volt-DC voltage
level is too low for the Aqua-Hot to operate properly. This
fault must be manually reset after the voltage level has
been restored to the 12 Volt-DC battery system. Reference
“Low Voltage Fault Indicator Light and Reset Button” infor-
mation below.
Low Voltage Fault Indicator Light and Reset Button:
The Aqua-Hot’s electronic controller must be manually
reset whenever the low battery voltage fault indicator light
has been activated.
The electric controller can be reset by turning OFF the
Diesel-Burner switch on the interior switch panel for ap-
proximately 60 seconds, then turning the switch back ON
by pressing the “Low Voltage Reset” button located on the
electric controller (use a thin, straight, non-metallic object
to access the reset button through the small hole on the
faceplate).
Overload Fault Indicator Light:
This indicator light will illuminate RED whenever one of
the following conditions have occurred:
1. The Aqua-Hot is off due to an electrical overload (i.e.,
short) in the main 12 Volt-DC power supply circuitry.
2. The Aqua-Hot is off due to a combination of high elec-
trical 12 Volt-DC power loads and a high surface tem-
perature of the electronic controller.
The Aqua-Hot will automatically restart once the elec-
toral overload (i.e., short) and/or high-heat condition is
corrected.

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Heating Zones Status Indicator Lights:
These five indicator lights (separately) will illuminate
GREEN whenever a zone thermostat, for each particular
zone, is calling for heat. The GREEN indicator lights also
indicate that 12 Volt-DC power is being supplied to the par-
ticular interior heating zone’s heat exchangers (i.e., fan mo-
tors).
If any of the five indicator lights illuminate RED, it indi-
cates that an electrical overload condition (i.e., short) has
occurred in a particular heating zone’s circuitry.
Pumps #1, #2, and #3 Indicator Lights:
These indicator lights (separately) will illuminate GREEN
whenever a circulation pump is operating. If any of the three
indicator lights illuminate RED, it indicates that an electrical
overload condition (i.e., short) has occurred in the particular
component’s circuitry.
Electric Heating Element Status Indicator Light:
This indicator light will illuminate GREEN whenever the
Aqua-Hot’s electric heating element is operating and provid-
ing heat to the Aqua-Hot’s boiler tank.
Please note that this light will only be active if the elec-
tric element switch is ON. If this indicator light illuminates
RED, it indicates an electrical overload condition (i.e., short)
has occurred in the electric heating element’s 12 Volt-DC.
Engine Preheat Pump Indicator Light:
The indicator light will illuminate GREEN whenever the
engine preheat circulation pump is operating. Please note
NOTE: Zone circulation pumps #1 and #2 are activated
whenever a zone thermostat “calls for heat”. The #3
boiler tank stir pump is activated whenever the domes-
tic water is being used on a continuous basis or the
heater is not up to operating temperature.
NOTE: The Low Temp Cutoff Light must be illuminated and
the heater must be up to operating temperature for the
heating zone status indicator lights to illuminate red or
green.
that this light will only be active if the engine preheat switch
is ON in conjunction with either the Diesel-Burner and/or
the electric element switch. If this indicator light illuminates
RED, it indicates an electrical overload condition (i.e., short)
has occurred in this particular component’s circuitry.
Tempering Valve
The Tempering Valve for the Aqua-Hot mixes the heated
domestic water from the boiler tank with cold domestic wa-
ter at the present ratio to reduce the risk of scalding. This
valve is located in the back of the Aqua-Hot unit. Reference
page 6 (part #19).
To locate the Tempering Valve, remove the access cover
page 6 (part #2) and then the thermostat access cover lo-
cated above the burner. Reference page 6 (part # 15). The
pink paint witness mark verifies that the Aqua-Hot is set at
the correct factory setting and did not get tampered with
during shipping or installation.
Verify that the Tempering Valve is set at the proper tem-
perature by using a digital thermometer at one of the hot
water faucets. The water temperature should range be-
tween 115°F to 123°F. If the correct temperature cannot be
set, please contact Aqua-Hot Heating Systems Technical
Support Department at 1-800-685-4298 for additional as-
sistance or visit the web site at www.aquahot.com.
NOTE: The Aqua-Hot’s VDC/VAC Control Thermostat will
automatically activate the Diesel-Burner and/or the electric
heating element ONLY if the Diesel-Burner and/or electric
element switch is in the ON position.
Figure 2
Troubleshooting Guide

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DATE SERVICE PERFORMED SERVICE CENTER
Owner’s Service Log

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DATE SERVICE PERFORMED SERVICE CENTER
Owner’s Service Log

2-YEAR LIMITED WARRANTY AQUA-HOT®
HYDRONIC HEATING SYSTEM
Aqua-Hot Heating Systems Inc. warrants the Aqua-Hot Heater to be free from defects in material
and workmanship under normal use and service for a period of two years on both parts and
labor commencing upon the original date of registration of the vehicle. Replacement parts are
warranted for the remainder of the Heater’s standard warranty coverage or for six months,
whichever is greater. The intent of this warranty is to protect the Heater’s end-user from such
defects, which would occur in the manufacturing of the product. Thus, problems due to
improper specifications, improper installations, improper use, the use of accessory parts or
parts not authorized by Aqua-Hot Heating Systems Inc., repair by unauthorized persons, and
damage or abuse of the Heater are specially excluded from warranty coverage.
For additional information or to obtain a warranty repair authorization, please contact the
Aqua-Hot Heating Systems Warranty Administrator at 1-800-685-4298 (8:00 AM to 5:00 PM
Mountain Standard Time) or visit www.aquahot.com.
My Comfort Zones are On-Board
Vehicle:
Purchased From:
Dealer Information:
Name:
Location:
Phone Number:
Heating System:
Serial Number:
Warranty
600SERIES
600D and 675D

7501 Miller Drive, Frederick, CO 80504
Visit us on line at www.aquahot.com
Call us at [phone] or [phone]
©2013 Aqua-Hot Heating Systems Inc. Printed In U.S.A.
600SERIES
600D and 675D
LTE-907-675 Rev. B